class Solution {
public:
 int dx[4] = {1, -1, 0, 0};
 int dy[4] = {0, 0, 1, -1};
    bool  vis[301][301];
    int m,n;
    int numIslands(vector<vector<char>>& grid) {
        int ret=0;
         m=grid.size(); n=grid[0].size();
        for(int i=0;i<m;i++)
        {
            for(int j=0;j<n;j++)
            {
                if(grid[i][j]=='1'&&vis[i][j]==false)
                {
                    ret++;
                    bfs(grid,i,j);
                }
            }
        }
        return ret;
    }

    void bfs(vector<vector<char>>& grid,int i,int j)
    {
        queue<pair<int,int>>q;
        q.push({i,j});
        vis[i][j]=true;
        while(q.size())
        {
            auto [a,b]=q.front();

            q.pop();
            for(int k=0;k<4;k++)
            {
                int x=a+dx[k];int y=b+dy[k];
                if(x>=0&&x<m&&y>=0&&y<n&&grid[x][y]=='1'&&!vis[x][y])
                {
                    q.push({x,y});
                    vis[x][y]=true;
                }
            }    
        }       
    }
};
